1. Field of the Invention
The present invention relates to an internal combustion engine and, more particularly, to an internal combustion engine having an improved combustion chamber design and method which effectively divides the chamber into two portions having a volume ratio of about 9 to 1 when the piston is at the top of its travel, thereby resulting in greater fuel efficiency at idle and very low power settings.
2. Description of the Related Art
There has been a long continuing effort to design internal combustion engines to be more fuel efficient and environmentally effective. See for example, U.S. Pat. No. 1,434,448, U.S. Pat. No. 2,632,432, U.S. Pat. No. 4,235,203, U.S. Pat. No. 4,359,027, U.S. Pat. No. 4,788,942, U.S. Pat. No. 5,163,395 and U.S. Pat. No. 5,195,486. All of these patents show combustion chambers of different shapes created by protrusions from or indentations in the top surface of a piston and/or various wall arrangements in the cylinder head.
In two-stroke engines, used extensively for outboard and inboard boat engines, motorcycles, personal watercraft and snowmobiles, power generation consists of a compression stroke where the piston travels up the cylinder to compress a charge either of air or of pre-mixed air and fuel. If just air is compressed, then fuel is injected. Ignition usually occurs before the piston reaches the top of its travel, called the top dead center (TDC), or at TDC. Simultaneously, the region under the piston, the crankcase, is able to draw in a new charge of air or an air-fuel mix. After ignition, the exploding mixture raises the temperature and pressure in the cylinder and forces the piston downwardly. This downward movement turns the crankshaft and also compresses the charge in the crankcase, beneath the piston. As the piston approaches its lowest position, the bottom dead center (BDC), an exhaust port is uncovered allowing the newly formed exhaust gases of the combustion process to leave the cylinder and then a moment later a transfer or inlet port is uncovered allowing a new charge of air or an air-fuel mix to enter into the cylinder. The new charge provides combustion material for the next power stroke and also helps expels exhaust gases in the cylinder. Often, the top of a piston in two stroke engines includes a deflector causing the new charge to be directed upwardly into the cylinder and around to the opposite side in a flow mechanism which is often called "cross-scavenging".
For a given size engine operating at a particular speed, the two-stroke engine is more powerful than a four-stroke engine since the two-stroke engine has twice as many power strokes per unit of time. Unfortunately, the fuel efficiency of a two-stroke engine is very likely to be lower than that of a four-stroke engine. Since the 1920s attempts have been made to optimize efficiency of two stroke engines and many different techniques have been utilized.
While efficiency of two stroke engines have improved over the years, continuing efforts are being made to further improve efficiency in an effort to produce an optimal engine.